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pch_uart: fix a deadlock when pch_uart as console

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When we use pch_uart as system console like 'console=ttyPCH0,115200',
then 'send break' to it. We'll encounter the deadlock on a cpu/core,
with interrupts disabled on the core. When we happen to have all irqs
affinity to cpu0 then the deadlock on cpu0 actually deadlock whole
system.

In pch_uart_interrupt, we have spin_lock_irqsave(&priv->lock, flags)
then call pch_uart_err_ir when break is received. Then the call to
dev_err would actually call to pch_console_write then we'll run into
another spin_lock(&priv->lock), with interrupts disabled.

So in the call sequence lead by pch_uart_interrupt, we should be
carefully to call functions that will 'print message to console' only
in case the uart port is not being used as serial console.

Signed-off-by: Liang Li <liang.li@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Liang Li 2013-01-19 17:52:10 +08:00 committed by Greg Kroah-Hartman
parent 64325a3be0
commit 384e301e35
1 changed files with 22 additions and 7 deletions
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29
drivers/tty/serial/pch_uart.c
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@ -1024,22 +1024,37 @@ static unsigned int dma_handle_tx(struct eg20t_port *priv)
static void pch_uart_err_ir(struct eg20t_port *priv, unsigned int lsr)
{
u8 fcr = ioread8(priv->membase + UART_FCR);
struct uart_port *port = &priv->port;
struct tty_struct *tty = tty_port_tty_get(&port->state->port);
char *error_msg[5] = {};
int i = 0;
/* Reset FIFO */
fcr |= UART_FCR_CLEAR_RCVR;
iowrite8(fcr, priv->membase + UART_FCR);
if (lsr & PCH_UART_LSR_ERR)
dev_err(&priv->pdev->dev, "Error data in FIFO\n");
error_msg[i++] = "Error data in FIFO\n";
if (lsr & UART_LSR_FE)
dev_err(&priv->pdev->dev, "Framing Error\n");
if (lsr & UART_LSR_FE) {
port->icount.frame++;
error_msg[i++] = " Framing Error\n";
}
if (lsr & UART_LSR_PE)
dev_err(&priv->pdev->dev, "Parity Error\n");
if (lsr & UART_LSR_PE) {
port->icount.parity++;
error_msg[i++] = " Parity Error\n";
}
if (lsr & UART_LSR_OE)
dev_err(&priv->pdev->dev, "Overrun Error\n");
if (lsr & UART_LSR_OE) {
port->icount.overrun++;
error_msg[i++] = " Overrun Error\n";
}
if (tty == NULL) {
for (i = 0; error_msg[i] != NULL; i++)
dev_err(&priv->pdev->dev, error_msg[i]);
}
}
static irqreturn_t pch_uart_interrupt(int irq, void *dev_id)